Antistatic photographic film



J. MARETTE ANTISTATIC PHOTOGRAPHIC FILM Filed June 30, 1925 22 /Tr'y Patented July 12, 1927.

UNITED STATES PATENT OFFICE.

JACQUES BAREME, or VINCENNES, FRANCE, AssIeNoE To ,rA'rHE CINEMA, ANCIENS ETABLISSEMENTS EATHE EnEnEs, or rAEIs, FRANCE.

ANTISTATIC rHo'roGnArmC Emu. i

Application med June 80, 1925, Serial No. 40,890, vand in France Hay 26, v192425.

Motion picture films wherein the support or backing consists of a material having nitrocellulose as a base, have a serious drawback from the fact that the film is 'easily electried when in contact with the parts of the apparatus serving either for the manufacture or for the utilization of the film. The electrifying of the film is made evident by the` characteristic formation on the' film of marks w vwhich are Vdue to electric sparks produced by static discharges; Such marks appear upon the ima-ge after developing, and cannot be eliminated.

Attempts have already been made to obl viate this electrifying eiect, and to manufacture films which are exempt from such discharges, these being. termed antistatic films. It has for instance been proposedto utilize the property possessed by certain cellulose compounds 'which become charged with electricity of contrary sign, and for this purpose a mixture of cellulose acetate and nitrocellulose, has been employed either to form the support of the film or to serve as an antistatic coating.

It has also been proposed to utilize as antistatic coating. ethylcellulose either alone or mixed with cellulose acetate oreniwtrocellulose.

- The aforesaid methods offer various drawbacks, and the object of the present invention is to obviate these drawbacks.

An embodiment of the invention is shown by way of example, on the drawing.

According to the invention the film, Whose 'bacln'ng vor support 1 consists of a substance having nitrocellulose as a base is coated upon the back, i. e. upon the face opposite that coated with the emulsion 2, with a coating 4 0 3 of a protectingand antistatic nature consisting of a substance having as a base plastic cellulose nitroacetate.

The cellulose nitroacetate which is a complex cellulose ester can be, but to a very7 slightly appreciable extent, electrified, and

especially when combined with softeners. In this event it forms an approved protecting substance for the nitrocellulose support, and prevents the latter from being electrified.

The said protecting and antistatic coating 3 having. cellulose nitroacetate as a base 1s applied in a very'thin coat upon the back of )the support of the film by means of a known solvent, and the photographic emule sion 2 is coated upon the other face, so that the support of the film will be entirely protected.

The said coating is prepared by dissolving cellulose nitroacetate in a solvent which will v also dissolve nitrocellulose, such as acetone so or the like; the amount of solvent used will depend upon the concentration and the thickness of the desired coating. To the said solution is added, in the usual proportions, the known softeners such as tricresylphosphate, triphenylphosphate, etc., which im artto the resulting product the desired fiexi ilit and incombustibility, and augment its antistatic qualities. y

The said coating may be prepared without the use of softeners, but it has been observed that the best results are obtained when the cellulose nitroacetate is rendered plastic.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1'. An antistatic film comprising a.4 film support, one face whereof is coated with sen sitiveemulsion, while its other face is coated with a coating comprising cellulose nitroacetate.

2. An antistatic Ifilm comprising a film support, one face whereof is coated with sensitive emulsion, while its other face is coated with a coating comprising plastic cellulose 35 nitroacetate.

In testimony whereof I have signed my i name to this Specification.

JACQUES MARETTE. 

